The invention relates to a motor-and-pump unit.
From U.S. Pat. No. 5,348,382, a hydraulic piston pump for an anti-lock system of a hydraulic vehicle brake system is known. The piston pump has a driving shaft, an eccentric element disposed on and rotatable by this shaft, and two pump pistons disposed to be displaceable diametrically to the shaft and thus in alignment with the eccentric element. The eccentric element is embodied as an inner bearing bush, shaft from sheet metal, and a thermoplastic support body between this inner bearing bush and the driving shaft. Roller bodies are disposed around the inner bearing bush, and in turn are surrounded by an outer bearing bush; the outer bearing bush transmits reciprocating motions, originating at the eccentric element and transmitted by the roller bodies to the outer bearing bush, to the pump pistons. An inner cylinder liner of a shaft bearing of the driving shaft is also embodied in one piece with the inner bearing bush of the eccentric element. The inner cylinder liner of the shaft bearing is likewise surrounded by cylindrical roller bodies, which in turn are also surrounded by an outer bearing bush, which rests in a housing of the piston pump. This shaft bearing generates only radial bearing forces, so that for axially fixing the position of the shaft, an axial bearing is needed in addition. This axial bearing may for instance be formed by one face end of the driving shaft and by an associated axial stop body, which makes this kind of axial bearing a slide bearing.
From international patent disclosure WO 98/16986, a motor-and-pump unit with an electric motor is known; the electric motor has a motor housing with two end walls, and in the end walls magnets and an armature with a shaft and two shaft bearings, at least one of which is embodied as a ball bearing with an outer ball bearing race and an inner ball bearing race and balls located between them; the outer ball bearing race is retained in a tubular bearing neck, which protrudes outward from one of the two end walls. This motor-and-pump unit also includes a pump, with a pump housing mounted on the end wall that has the bearing neck; at least one pump piston can be displaced in this pump housing, in a transverse alignment with the longitudinal axis of the shaft, by means of an eccentric element, disposed inside the pump housing, that is secured to one shaft end protruding from the ball bearing and forms a raceway for cylindrical roller bodies; the roller bodies are surrounded by an outer roller bearing bush, and the outer roller bearing bush, upon rotation of the shaft with the attendant reciprocating motions of the eccentric element, displaces the pump pistons. The eccentric element is disposed at an axial spacing from the inner ball bearing race. A collar, for example, protruding radially inward from the ubular bearing neck dips into this axial spacing. On the one hand the collar forms an axial stop for the outer ball bearing race, and on the other, the collar acts as an axial stop face for the outer roller bearing race of the eccentric element. This motor-and-pump unit is once again a component of a hydraulic vehicle brake system, and accordingly it cannot be precluded that the load on the eccentric element and thus the bending stress on the shaft, and its elastic warping, will be caused by the high brake pressure to be generated. Since as already noted this motor-and-pump unit is a component of a vehicle, its individual parts should on the one hand be lightweight but on the other so rigid that elastic deformation of the components will not make unpleasant noise.